[Intel-gfx] [PATCH] drm/i915/gem: Pin gen6_ppgtt prior to constructing the request

[Chris Wilson]

All pinning must be done prior to i915_request_create, to avoid
timeline->mutex inversions.

Here we slightly abuse the context_barrier_task stages to utilise the
'skip' decision as an opportunity to acquire the pin on the new ppgtt.
Consider it s/skip/prepare/. At the moment, we only have on user of
context_barrier_task, so it might be worth breaking it down for the
specific task of set-vm and refactor it later if we find a second
purpose.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/gem/i915_gem_context.c | 18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_context.c b/drivers/gpu/drm/i915/gem/i915_gem_context.c
index 9f1dc96b10a6..9d8d75765ee4 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_context.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_context.c
@@ -1141,8 +1141,6 @@ static int emit_ppgtt_update(struct i915_request *rq, void *data)
 		*cs++ = MI_NOOP;
 		intel_ring_advance(rq, cs);
 	} else {
-		/* ppGTT is not part of the legacy context image */
-		gen6_ppgtt_pin(i915_vm_to_ppgtt(vm));
 	}
 
 	return 0;
@@ -1150,10 +1148,20 @@ static int emit_ppgtt_update(struct i915_request *rq, void *data)
 
 static bool skip_ppgtt_update(struct intel_context *ce, void *data)
 {
+	if (!test_bit(CONTEXT_ALLOC_BIT, &ce->flags))
+		return true;
+
 	if (HAS_LOGICAL_RING_CONTEXTS(ce->engine->i915))
-		return !ce->state;
-	else
-		return !atomic_read(&ce->pin_count);
+		return false;
+
+	if (!atomic_read(&ce->pin_count))
+		return true;
+
+	/* ppGTT is not part of the legacy context image */
+	if (gen6_ppgtt_pin(i915_vm_to_ppgtt(ce->vm)))
+		return true;
+
+	return false;
 }
 
 static int set_ppgtt(struct drm_i915_file_private *file_priv,
-- 
2.24.0